Watersports involving powered watercraft have enjoyed a long history. Waterskiing's decades-long popularity spawned the creation of specialized watercraft designed specifically for the sport. Such “skiboats” are optimized to produce very small wakes in the water behind the watercraft's hull, thereby providing the smoothest possible water to the trailing water skier.
More recently, watersports have arisen which actually take advantage of, and benefit from, the wake produced by a watercraft. Wakesurfing, wakeboarding, wakeskating, and kneeboarding all use the watercraft's wake to allow the participants to perform various maneuvers or “tricks” including becoming airborne.
As with waterskiing “skiboats”, specialized watercraft known as “wakeboats” have been developed for the wakesurfing, wakeboarding, wakeskating, and/or kneeboarding sports. Contrary to skiboats, however, wakeboats seek to enhance (rather than diminish) the wake produced by the hull using a variety of techniques.
Both skiboats and wakeboats have long suffered from a lack of maneuverability, a consequence of their optimization for straight-line driving to provide the best “pull” for watersport participants. The installation of tracking fins on the keel of the hull, the use of a propeller with a fixed orientation relative to the hull, and the placement of the rudder relative to the propeller provide excellent straight-line tracking but severely impair the ability of the watercraft to turn, particularly at the slow speeds encountered during docking, trailering, and recovery of someone in the water. Backing up (going in reverse) can be even more challenging since the rudder is no longer downstream of the propeller.
Seeking to address these limitations, some in the marine industry have borrowed the concept of “thrusters” from cruise ships and other extremely large vessels. These thrusters are essentially sideways-mounted propellers that rotate the vessel by applying lateral thrust to the hull, obviating sole dependency upon the main propeller and rudder for hull rotation.
These previous attempts have required elaborate and complex schemes to integrate a thruster into the watercraft hull, and associate the operation of a thruster with existing steering apparatuses.
As a first example, U.S. Pat. No. 5,016,553 to Spencer requires its “thruster propeller” 11 (C4 L11) to be mounted external to the hull (Spencer FIGS. 2, 3, 4, 5, and 6). This in turn requires modification to otherwise standard propulsion and steering subsystems.
As another example, U.S. Pat. No. 10,331,137 to Miller et. al requires, and illustrates, its “thruster” 14 in FIG. 1 to be “distinct from the primary steering mechanism” (C1 L58) “such as a rudder” (C1 L54). Miller then describes its complex and elaborate schemes required to associate its thruster 14 with the primary steering mechanism 22 of the watercraft.
Some thrusters have been mounted to the outside of the transom of the hull. Such arrangements expose the thruster to damage and maintenance challenges resulting from long-term immersion in water. They also expose passengers in the surrounding water to injury from the thruster. External mounting often also causes undesireable effects due to thruster interaction with other watercraft components that are mounted on or near the transom.
Some thrusters have been mounted in a tube-like passage through the hull. The structural and waterproofing difficulties of such hull penetrations speak for themselves, to say nothing of the hydrodynamic losses incurred by disrupting the otherwise smooth surface of a well-designed hull.
Small watercraft thrusters suffer from the same problem as traditional high volume ballast pumps: Their electrical power requirements overwhelm the electrical capabilities of skiboats and wakeboats. It is not uncommon for such thrusters to have peak current requirements in the hundreds of amperes, while the alternators on the corresponding inboard engines typically have a maximum current output of 100 amperes—and then only when the engine is running at a relatively high RPM that is optimal for the alternator.
Given the rapidly expanding interest in, and market for, wakeboats, their difficulties in maneuvering represent an increasingly serious limitation for their manufacturers, dealers, and operators. An invention that improves this maneuverability while being compatible with the engines used in such watercraft would improve safety, comfort, confidence, and market opportunities for everyone in the industry.